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Ministério da Ciência, Tecnologia e Ensino Superior Instituto de Meteorologia, I. P. Rua C – Aeroporto de Lisboa Lisboa – Portugal Tel.: (351) Fax: (351) URL: Raster calculator Allows for computing a combination of logical and algebraic expressions Example: Calculate the arithmetic mean LST values for a specific day (using hourly sample) 24 raster files each with the LSA SAF LST product for the hourly timeslots GRASS GIS Approach #1: Using only cells where there is enough data for the whole day (In GRASS, any math performed with NULL cells always results in a NULL value for these cells Approach #2: Using all the cells where there is at least one value in the day